Overview
Hablator is an advanced GPL'ed chat script written in PHP and Javascript.
It offers all of the features you could want in a chat script, while maintaining low server requirements, low client requirements, exceptional speed, and simple installation.

Features

Translate chat text to communicate with those who speak other languages.

See when others start and stop typing a message

Upload files easily during discussions

Allow multiple discussion "topics" to let users discuss different things at the same time, and not need to install multiple chat rooms and/or prefix each message with the discussion topic. This allows users to engage in one or more topics, and follow others they are interested in

Choose whether to use a FlatFile backend, a MySQL backend, or a SQLite backend

Talk to people who don't have Javascript support, or to people with text-only browsers, with compatibility mode